U.S. patent number 4,093,759 [Application Number 05/658,789] was granted by the patent office on 1978-06-06 for glass container coated with polyurethane.
This patent grant is currently assigned to Toyo Ink Manufacturing Co., Ltd.. Invention is credited to Akira Ikeda, Yukifumi Mashimo, Michihisa Naito, Akira Otsuki.
United States Patent |
4,093,759 |
Otsuki , et al. |
June 6, 1978 |
Glass container coated with polyurethane
Abstract
A process for preventing the scattering of glass fragments in
the event of the bursting of a glass container such as a bottle,
which comprises coating the surface of the glass container with a
resin composition in a thickness of at least 100 microns, said
composition comprising a dispersion of (A) a powder with a particle
diameter of about 1 to 100 microns of a solid compound capable of
reaction with (B) upon heating to form a higher molecular weight
cured product, in (B) a normally liquid urethane prepolymer having
a molecular weight of at least 400 per isocyanato group, and being
capable of forming a film having a tensile strength of at least 300
kg/cm.sup.2 and a percent elongation of at least 200%.
Inventors: |
Otsuki; Akira (Tokyo,
JA), Naito; Michihisa (Tokyo, JA), Mashimo;
Yukifumi (Tokyo, JA), Ikeda; Akira (Tokyo,
JA) |
Assignee: |
Toyo Ink Manufacturing Co.,
Ltd. (Tokyo, JA)
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Family
ID: |
26464413 |
Appl.
No.: |
05/658,789 |
Filed: |
February 17, 1976 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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428586 |
Dec 26, 1973 |
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Foreign Application Priority Data
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Dec 23, 1972 [JA] |
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47-128840 |
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Current U.S.
Class: |
428/34.7;
215/12.2; 215/DIG.6; 427/389.7; 428/327; 428/339; 428/425.6 |
Current CPC
Class: |
B65D
23/0814 (20130101); C03C 17/322 (20130101); Y10T
428/31601 (20150401); Y10T 428/254 (20150115); Y10T
428/269 (20150115); Y10T 428/1321 (20150115); Y10S
215/06 (20130101) |
Current International
Class: |
B65D
23/08 (20060101); B65D 23/00 (20060101); C03C
17/32 (20060101); C03C 17/28 (20060101); B65D
001/02 () |
Field of
Search: |
;427/385A
;428/35,327,339,425 ;260/75NH,75NP,77.5PM ;215/DIG.6,12R |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Gwinnell; Harry J.
Assistant Examiner: Childs; Sadie L.
Attorney, Agent or Firm: Sughrue, Rothwell, Mion, Zinn and
Macpeak
Parent Case Text
This is a continuation of application Ser. No. 428,586, filed Dec.
26, 1973, now abandoned.
Claims
What is claimed is:
1. A glass container carrying on the surface thereof a single layer
coating of a transparent non-tacky film in a thickness of at least
100 microns and having a tensile strength of at least 300
kg/cm.sup.2 and a percent elongation of at least 200%, said film
being a cured high molecular weight compound formed by the reaction
of a powder having a particle diameter of about 1 to 100 microns of
a solid compound having a melting point of more than 20.degree. C.
selected from the group consisting of melamine, benzoguanamine, and
acetoguanamine with 0.9 to 1.5 equivalents per equivalent of said
powder of a urethane prepolymer which is normally liquid and has at
least 2 isocyanate groups and has a molecular weight of at least
400 per isocyanate group, said coating having been cured at a
temperature of 180.degree. to 200.degree. C.
2. The container of claim 1 wherein said urethane prepolymer is a
reaction product of 1 equivalent of a polyol selected from the
group consisting of polypropylene glycol, polyethylene glycol
adipate, polybutylene glycol adipate, polytetramethylene glycol, a
polyester-polyol, trimethylolpropane, 1,4-butylene glycol,
trimethylhexanediol, and 2,2,4-trimethyl-1,3-pentanediol, and 2
equivalents of a diisocyanate selected from the group consisting of
tolylene diisocyanate, hexamethylene diisocyanate, isophorone
diisocyanate, 4,4-diphenylmethane diisocyanate, xylylene
diisocyanate and naphthalene diisocyanate.
3. The container of claim 1 wherein said normally solid compound is
a powder of melamine or benzoguanamine having a particle diameter
of 3 to 10 microns.
4. The container of claim 1 wherein the ratio between said urethane
prepolymer and said solid compound is an equivalent ratio.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a process for preventing the scattering
of glass fragments resulting from the bursting of a glass article
such as a bottle by coating the surface of the glass article with a
novel urethane resin composition. The process is also effective for
protecting the surface of the glass article and for compensating
for a reduction in strength ascribable to surface scratches or
similar defects.
2. Description of the Prior Art
In order to increase the resistance of glass to bursting, a resin
layer is usually coated on a glass surface. Such a resin coating
has been applied to safety glass, glass bottles and photographic
flash bulbs. Since the bursting of glass is accelerated by surface
scratches on the glass article, the crystallization of the surface
layer and abrupt changes in temperature, the coating of the glass
surface with a resin is effective for preventing the strength of
glass from decreasing.
However, coating materials for preventing scattering of glass
fragments in the event of bursting of a glass bottle filled with
carbonated beverages, beer or a similar gas-forming beverages
require different properties from those used for reinforcing or
surface-protecting of glass articles. According to the invention of
our copending U.S. Pat. application Ser. No. 341,197 filed on Mar.
14, 1973 now abandoned, the coating resin for preventing the
scattering of glass fragments caused by the bursting of a filled
glass container such as a bottle (for brevity, hereinafter the
description will be directed to the coating of bottles) must have
an adequate tensile strength (on glass bursting), an adequate
percent elongation (on glass bursting) and good adherence to the
glass surface. All of these physical properties need not be
superior at the same time, because their relationship, especially
the relationship between the tensile strength and the percent
elongation, is more important for obtaining favorable results.
More specifically, a very high tensile stength is not always
required, and a suitable value can be determined in accordance with
the value of the percent elongation. Thus, high tensile strength is
required if the percent elongation is low, and even a relatively
low tensile strength can be effective if the percent elongation is
high. The lower limit of the tensile strength is about 50
kg/cm.sup.2 and that of the percent elongation, about 100%. The
preferred ranges of the tensile strength and of the elongation are
about 300 to about 600 kg/cm.sup.2 and about 200 to 600%,
respectively.
An effective thickness of the resin coating is more than about 50
microns if the resin satisfies the above-described requirements,
and preferably a thickness of from about 100 to about 200 microns.
The optimum thickness is determined in accordance with the glass
wall thickness and the inner pressure which the glass bottle to be
coated will generally experience.
Methods of reinforcing a glass bottle by coating a film on the
surface of a bottle are well known. For example, coating resins for
glass bottle are disclosed in U.S. Pat. No. 3,178,049. This patent
discloses a method for reinforcing a glass bottle. In contrast, the
present invention relates to a method for preventing the scattering
of glass fragments resulting from the bursting of a glass bottle by
coating the surface of the bottle with a film of a novel urethane
resin composition. Accordingly, this invention is quite different
from the above-described patent. Furthermore, while a polyurethane
resin is exemplified in U.S. Pat. No. 3,178,049 as a resin that can
be used, no specific description appears with respect to the nature
of the polyurethane resin used.
Many compositions are known for forming polyurethane resin films.
For example, U.S. Pat. No. 3,428,609 discloses a process for
manufacturing a solution in an organic solvent of a polyurethane.
Some of the urethane resin films obtained from the solution possess
the physical properties required of films. The composition
disclosed in the above patent, however, contains an organic
solvent, and it is generally known that compositions requiring an
organic solvent are unfavorable since not only are they hazardous
to the health of the working personnel but also cause
pollution.
A solvent-free polyurethane resin composition is disclosed, for
example, in U.S. Pat. No. 3,428,610. This patent describes a method
for producing a cross-linked polyurethane, which comprises reacting
an intermediate (urethane prepolymer) having a free NCO group with
an aromatic diamine as a chain extending agent to form a highly
elastic urethane resin. Although the composition thus prepared is
suitable for casting, it is not suitable for coating. In addition,
the curing after casting is effected by the action of moisture in
the air, and from two to eight days are required for curing.
The invention described in our previous application includes a
process for coating a glass bottle using solvent-free urethane
resin compositions. However, these compositions are of a reactive
two-package type having the defect of short storage period (or pot
life).
SUMMARY OF THE INVENTION
According to this invention, a urethane resin composition free from
solvent and having a long pot life is used. The film prepared from
this resin meets the physical requirements for preventing the
scattering of glass fragments in the event of the bursting of the
bottle. The composition specifically comprises a dispersion of (A)
one equivalent of a powder with a particle diameter of 1 to 100
microns of a solid compound having a melting point of more than
20.degree. C capable of reaction with (B) upon heating to form a
higher molecular weight cured product in (B) 0.9 to 1.5 equivalents
of a normally liquid urethane prepolymer having at least two
isocyanato groups in the molecule and having a molecular weight of
at least 400 per isocyanato group. The cured composition provides a
film having a tensile strength of at least 300 kg/cm.sup.2 and
percent elongation of at least 200%.
DETAILED DESCRIPTION OF THE INVENTION
U.S. Pat. No. 3,726,835 discloses a casting composition comprising
a mixture of a liquid urethane prepolymer and melamine or
dicyandiamide. Since this composition is used for casting, it is
incapable of forming a film unlike the composition used in the
present invention. Furthermore, since the tensile strength and
percent elongation of the film are not required in a composition
for casting as used in this U.S. patent there is an important
difference between the composition disclosed in this U.S. patent
and the composition used in the process of the present invention.
In U.S. Pat. No. 3,726,835, the mixing ratio between the prepolymer
and melamine or dicyandiamine is such that 1/3 to 4 equivalents of
the prepolymer is used per equivalent of melamine or dicyandiamide,
whereas in the present invention, the required physical properties
of the film can be obtained only when the proportion of the
prepolymer is within 0.9 to 1.5 equivalents per equivalent of the
component (A). In U.S. Pat. 3,726,835, it is not necessary that the
particle diameter of the powder solid compound to be reacted be
restricted but in the present invention it is essential that the
particle diameter of the powder be not more than 100 microns in
order to accelerate the formation and curing rate of the film.
Furthermore, the molecular weight of the urethane prepolymer is not
restricted in U.S. Pat. No. 3,726,835, but in the present
invention, the urethane prepolymer should have a molecular weight
of at least 400 per isocyanato group in order to obtain a suitable
film percent elongation for the effects of the present
invention.
Since the composition used in this invention is solvent free, no
pollution problems result. In addition, the composition of this
invention has a long pot life, e. g., about 3 to 6 months, at room
temperature and good workability, and rapidly reacts upon heating,
e. g., at temperatures of about 180.degree. to 200.degree. C for
about 10 minutes, after coating to form a transparent urethane
resin coating. The resulting film has a tensile strength of at
least 300 kg/cm.sup.2 and percent elongation of at least 200%.
Further, the film thus obtained has an excellent abrasion
resistance. Therefore, a smaller deterioration in the physical
strength during transport and shipping, treatment or the like
results for the glass containers produced in accordance with the
present invention, and further the number which can be recovered
and reused can be increased by a factor of 3 or 4 times comparing
to that of the conventional glass containers.
The urethane prepolymer which is used for preparing the coating
composition in accordance with this invention is a reaction product
of 1 equivalent of a polyol having a molecular weight of about 250
to 1500 per one hydroxy group capable of having a molecular weight
of at least 400 per isocyanato group after reaction with an
isocyanate, such as polypropylene glycol, polyethylene glycol
adipate, polybutylene glycol adipate, polytetramethylene glycol, a
polyester-polyol, 2,2,4-trimethyl-1,3-pentanediol, trimethylol
propane, 1,4-butylene glycol or trimethylhexane diol with 2
equivalents of a diisocyanate having a molecular weight of about 90
to 130 per isocyanato group such as tolylenediisocyanate,
isophorone diisocyanate, hexamethylene diisocyanate, xylylene
diisocyanate, 4,4'-diphenylmethane diisocyanate or naphthalene
diisocyanate. This urethane prepolymer is a liquid at room
temperature and forms a urethane resin upon pg,8 an increase in its
molecular weight.
This urethane prepolymer can be prepared by heating 2 equivalents
of the diisocyanate in a nitrogen gas stream to 70.degree. to
80.degree. C, adding 1 equivalent of the polyol dropwise over a
period of about 1 hour with stirring, and reacting them further for
30 minutes to 2 hours after the polyol has been added.
The solid component of the coating composition used in the present
invention is one capable of reacting with the above described
liquid component upon heating thereby increasing the molecular
weight of the prepolymer, and includes, for example, melamine,
benzoguanamine, acetoguanamine, dicyandiamide, an aromatic diamine
having a melting point of about 50.degree. C., a polyamine,
bisphenol A, an epoxy intermediate, pentaerythritol, trimethylol
propane, trimethylol ethane, or an acrylic or vinyl polymer
containing a functional group such as a hydroxyl group, an amino
group or a carboxyl group. The use of the powdery solid component
contributes to the inhibition of the reaction and thereby curing at
room temperature and affords a long pot life. In order to obtain a
feasible rate of reaction by heating, the size of the powder
particles is of importance. If the particle diameter is large, the
reaction requires long periods of time, and a uniform film cannot
be obtained.
Investigations of the inventors have shown that in order to attain
a rapid and feasible reaction rate and to obtain a uniform coating,
the particle diameter of the powder should not be greater than 100
microns. It has been found that some of the solid component may be
melted by heating after coating and react, but if the particle size
of the powder is adjusted to not greater than 100 microns, the
solid component undergoes reaction even at a temperature below its
melting point to form a uniform film. This discovery was made after
investigating the relation between the particle diameter of the
solid component and the pot life of the resulting composition, the
heating temperature for inducing this reaction and the uniformity
of the film, etc. The optimum particle diameter differs depending
upon the types of the liquid component and the solid component
used, but is generally about 1 to 100 microns. In many cases, the
optimum particle diameter is 3 to 10 microns. By adjusting the
particle diameter, the heating temperature for curing does not
always need to be above the melting point of the solid component,
and lower temperatures near the melting point can also induce the
curing reaction to form a uniform transparent film.
It is necessary that the ratio of the solid component and the
urethane prepolymer be about equivalent ratio, and it is possible
to use 0.9 to 1.5 equivalents, of the prepolymer per equivalent of
the solid component. Clear films cannot be obtained from
compositions in which the proportion of the prepolymer is less than
0.9 equivalent, and the resulting films have insufficient
elongation. If, on the other hand, the proportion of the urethane
prepolymer is above 1.5 equivalents, the resulting film can be
highly elongated, but the film remains tacky and the film also has
insufficient tensile strength.
The molecular weight of the prepolymer must be at least 400,
preferably 400 to 3,000, per isocyanato group, and films obtained
from compositions in which the prepolymer has a molecular weight
lower than this have insufficient elongation properties.
The composition to be used in this invention may further contain
other ingredients such as fillers, pigments, other resins, etc. so
long as they do not lead to the loss of these essential
characteristics.
The following Examples and Comparative Examples illustrate the
present invention in greater detail. Unless otherwise indicated all
parts and percents are by weight.
EXAMPLE 1
A 8:2 by weight mixture (30.7g) of 2,4-tolylene diisocyanate and
2,6-tolylene diisocyanate was maintained at 80.degree. C in a
nitrogen gas stream with stirring, and a mixture consisting of
36.8g of PPG 1000 (a polypropylene glycol having a molecular weight
of about 1000) and 17.7g of PPG 400 (a polypropylene glycol having
a molecular weight of about 400) was added dropwise over the course
of 1 hour. The reaction was continued for an additional 30 minutes.
Then, 14.8g of a 1:1 mixture of melamine pulverized to an average
particle size of 10 microns and PPG 1000 was added, and the
resulting mixture was stirred at 70.degree. C for 1 hr. to obtain a
coating composition having a viscosity (20.degree. C) of 100,000
centipoises. Although the melting point of melamine is 260.degree.
C, if the particle size of the melamine is adjusted to not more
than 50 microns, it reacts with the prepolymer at a temperature
below 200.degree. C to form a uniform film as a result of curing in
about 10 minutes. Since in this Example, the particle diameter of
the melamine was 10 microns, the curing could be performed at
180.degree. C in 10 minutes. The film obtained from the composition
in this Example has a tensile strength of 400 kg/cm.sup.2 and
percent elongation of 200%.
Ten grams of the resulting composition was coated on the surface of
a beer bottle, and heated for 10 minutes at 180.degree. C to form a
coating. Since this bottle had a tough surface coating of urethane
resin having a thickness of 200 microns, the coated bottle had
resistance to damage or injury. When this bottle with an inner
pressure of 5kg/cm.sup.2 was dropped onto a concrete floor from a
height of 75 cm to break the bottle and evaluate the coating, no
scattering of glass fragments was observed.
EXAMPLE 2
Isophorone diisocyanate (39.3g) was maintained at 70.degree. C in a
nitrogen gas stream with stirring, and a mixture of 44.2 g of
polyethylene glycol adipate having a hydroxyl value of 224 and
0.01g of dibutyl tin dilaurarte was added dropwise over the course
of 1 hour. The reaction was continued for an additional 2 hours
after the addition. Then, the reaction mixture was cooled to
50.degree. C, and 16.5g of benzoguanamine pulverized to an average
particle diameter of 3 microns was added. The mixture was stirred
using a high speed mixer to form a coating composition having a
viscosity (50.degree. C) of 5000 centipoises. A film obtained from
this composition had a tensile strength of 350 kg/cm.sup.2 and
percent elongation of 300%.
Ten grams of this composition was coated on the surface of a beer
bottle, and heated at 200.degree. C for 10 minutes to form a
uniform coating. When this bottle was tested in the same way as
described in Example 1, similar good results were obtained.
EXAMPLE 3
2,4-Tolylene diisocyanate (26.4g) was maintained at 80.degree. C in
a nitrogen gas stream with stirring, and a mixture of 37.9g of
polybutylene glycol having a hydroxyl value of 112 and 19.0g of
polybutylene glycol adipate having a hydroxyl value of 224 was
added dropwise over the course of 1 hour. Then, the reaction was
continued for an additional one hour. The reaction mixture was then
cooled to 50.degree. C, and 16.7g of bisphenol A pulverized to an
average particle size of 5 microns was added. The mixture was
stirred using a high speed mixer to form a coating composition
having a viscosity of 3000 centipoises at 50.degree. C. A film
obtained from this composition had a tensile strength of 300
kg/cm.sup.2 and percent elongation of 200%.
Ten grams of this composition was coated on the surface of a beer
bottle, and heated at 180.degree. C for 10 minutes to form a cured
coating. When this bottle was tested in the same way as described
in Example 1, similar good results were obtained.
EXAMPLE 4
2,4-Tolylene diisocyanate (27.9g) was heated at 80.degree. C in a
nitrogen gas stream with stirring, and 66.6g of polytetramethylene
glycol having a hydroxyl value of 135 was added dropwise over the
course of 1 hour. The stirring and heating were continued for an
additional one hour, and then the reaction mixture was cooled to
room temperature (about 20.degree. to 30.degree. C). 5.5g of
powdered pentaerythritol having an average particle diameter of 100
microns was added, and the mixture was stirred using a kneader to
form a coating composition having a viscosity (20.degree. C) of
10,000 centipoises. This composition had a pot life of 3 months,
and a film obtained from this composition had a tensile strength of
400 kg/cm.sup.2 and percent elongation of 250%.
This composition was coated on a beer bottle in the same way as
described in Example 1, and similar effects were obtained.
COMPARATIVE EXAMPLE 1
A coating composition was prepared in the same way as described in
Example 2 except that the amount of isophorone diisocyanate was
changed to 49.6g, 29.6g of a polyol composed of glycerol and
polypropylene oxide of a molecular weight of 400 (TG 400, a
trademark produced by Nippon Soda Co., Ltd.) was used instead of
the 44.2g of the polyethylene glycol adipate, and the amount of
benzoguanamine was changed to 20.8g. A film obtained from this
composition was transparent and had a tensile strength of 200
kg/cm.sup.2. However, its percent elongation was only 10%, and the
use of this composition as in the present invention failed to
provide the desired effect. This is because TG 400 had a molecular
weight of 400/3 per hydroxyl group, and the resulting prepolymer
had a molecular weight of 355 per isocyanato group which is less
than the 400 required in this invention.
COMPARATIVE EXAMPLE 2
Example 2 was repeated except that the amount of benzoguanamine was
increased to 33g (thus reducing the equivalent amount of the
prepolymer to 1/2). A film obtained from this composition did not
become clear even when heated at 200.degree. C for 10 minutes. It
was useless in the present invention.
COMPARATIVE EXAMPLE 3
Example 1 was repeated except that the amount of the mixture of
14.4g of melamine and 7.4g of PPG 1000 was used such that the 1/2
equivalent of the prepolymer was used. A film obtained from this
composition as non-transparent and had a tensile strength of 60
kg/cm.sup.2 and percent elongation of 80%. The use of this
composition in this invention failed to attain the desired
effect.
COMPARATIVE EXAMPLE 4
Example 1 was repeated except that a mixture of 3.7g of melamine
and 7.4g of PPG 1000 was used instead of 14.8g of the mixture of
melamine and PPG 1000 in a ratio of 1:1 (thus increasing the
proportion of the prepolymer to 2 equivalents). A film obtained
from this composition had percent elongation of 500%, but a tensile
strength of only 100 kg/cm.sup.2. The surface of the film remained
tacky, and the composition could not be used for coating
purposes.
While the invention has been described in detail and with reference
to specific embodiments thereof, it will be apparent to one skilled
in the art that various changes and modifications can be made
therein without departing from the spirit and scope thereof.
* * * * *